Epiglottic Abnormalities in Nonracehorses: A Review

When a riding horse develops a cough or a runny nose, or when he begins having trouble making it through a previously easy workout, owners often seek a cause and a cure. And while respiratory ailments such as a lower respiratory disease might seem a likely culprit in these cases, a team of University of Pennsylvania researchers suggests that sometimes such clinical signs can be linked to epiglottic abnormalities. In a recently completed study the team characterized these epiglottic problems—which are commonly detected in racehorses—and their impact on nonracehorses.

"To our knowledge, clinical abnormalities and outcome of treatment in mature nonracehorses with epiglottic abnormalities have not been reported previously," said Eric J. Parente, DVM, Dipl. ACVS, associate professor of surgery at the New Bolton Center campus of the University of Pennsylvania's School of Veterinary Medicine, in Kennett Square, Pa.

When a horse swallows food or water, the epiglottis (a movable, leaf-shaped piece of cartilage located at the base of the tongue and above the soft palate) covers the opening of the larynx to ensure that food and water do not enter the trachea, but instead pass into the esophagus. Parente and Maia R. Aitken, DVM, a resident in the department of clinical studiesat New Bolton, listed some of the most common epiglottic abnormalities found in racehorses:

Epiglottic entrapments (when the epiglottis becomes trapped by the aryepiglottic folds of tissue and cannot move);

Epiglottic hypoplasia (incomplete development of the epiglottis);

Subepiglottic cysts (a cyst on or near the epiglottis);

Subepiglottic granulomas (tissue similar to "proud flesh" in a wound, under the epiglottis, often caused by some sort of trauma to the area);

Epiglottitis (inflammation of the epiglottis); and

Epiglottic abscesses.

To examine the impact of epiglottic abnormalitites on the respiratory function of nonracehorses, the team performed a retrospective study employing 23 mature horses (those more than eight years of age) with such anomalies. Referring veterinarians had examined these horses previously before New Bolton admission from April 1990 to August 2009. The horses (16 geldings and 7 mares of six breeds) were used for a variety of disciplines, including pleasure riding, all-purpose riding, dressage, show jumping, polo, and pleasure driving. Four of the horses were retired at the time of referral.

The team reviewed the data to determine the most common clinical signs, endoscopic findings, treatments, and outcomes associated with these abnormalities.

All of the horses that displayed exercise intolerance also produced abnormal sounds during exercise, Parente noted, and coughing was the only clinical sign displayed by seven of the 16 horses examined for coughing. He added that one horse did not exhibit any clinical signs of upper respiratory disease, but a veterinarian had discovered an epiglottic entrapment during an unrelated endoscopic examination.

Through the records of endoscopic examinations performed on the 23 horses, the researchers discovered that the most common epiglottic abnormality in the study horses was epiglottic entrapment, present in 13 horses. Seven of the 23 horses had subepiglottic granulomas, and three had subepiglottic cysts. None of the horses were diagnosed with epiglottic hypoplasia, epiglottitis, or epiglottic abscesses.

Treatment and Outcome

All 23 horses were treated with a variety of surgical methods and only one horse required a follow-up surgical treatment.

Parente and Aitken obtained follow-ups on all the horses (either through re-examination or through phone discussions with the owners):

In 17 of 23 horses, clinical signs had resolved and those horses actively working successfully returned to their previous level of work; The team noted that one of these horses underwent a second procedure to correct an epiglottic entrapment, however the second procedure proved successful;

Clinical signs had partially resolved in four horses, however all of their owners reported the animals returned to their previous level of work; and

Resolution of clinical signs was not achieved in two horses that had undergone subepiglottic membrane resection via laryngotomy. These horses were noted to have "persistent dorsal displacement of the soft palate" two months later.

"Older nonracehorses can have epiglottic abnormalities, and an endoscopic examination of the airway should be part of the workup for a horse that is coughing," Parente advised horse owners. "Don't just think 'lower airway disease' and put the horse on medication without having a better idea of what is causing the problem."

The study, "Epiglottic abnormalities in mature nonracehorses: 23 cases (1990-2009)," was published in the June 15 Journal of American Veterinary Medicine. The abstract is available online.

About the Author

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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